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Need schematic: 60-LED analog seconds-only clock


I built a "barn-door" tracker to take photos of planets and stars so that they are tracked (i.e they appear as dots, not trails). See http://en.wikipedia.org/wiki/Barn_door_tracker if you want more info about  trackers of this type.

My tracker can be seen in the first two photos here: http://www.tjimaging.com/ted/astro.htm

These devices depend upon the user manually turning a knob at exactly one rpm for as many as fifteen minutes. This is (very) tedious, but gets good results. The biggest difficulty is in keeping the proper rate of knob-turning. I use a stopwatch timer and have a pointer on the knob so I can manually match each second as it goes by. This has to be done in the *dark*, though, for obvious reasons! So there's an additional problem of lighting the dial and stopwatch.

My idea would be to affix a steady red LED to the end of the knob pointer and to use an analog clock consisting of 60 red LEDs arranged in a circle around the knob. Only one LED would be lit at a time, starting at 12 o'clock position, and advancing one LED at a time, clockwise, and keeping each LED lit for one second. This arrangement would let me simply match the knob's steady LED with the currently-lit one and thus makes manual matching of the "second hand" visually easy.

I expect a 555 timer circuit (powered by battery, not A/C, for portability) could handle this task, but I don't know enough about electronics to know for sure. I'd like to keep the cost lower than it would be if an Arduino-based circuit were used.

I've also never made a custom printed circuit board, but I'm game to try after building a successful breadboard.

I just need a schematic!  Thanks, all.

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I used to make drivers for these things commercially, with little battery operated AC motors, that ran off a crystal - they'd run for a week on 4 AAs
tjerome (author)  steveastrouk6 years ago
@steveastrouk: I'm aware of the motor-driven versions, but for this project I want a manually-driven system. Thanks, though!
Ted
Well, are you happy to use a microcontroller ? I have a solution for you if you can.

Steve
tjerome (author)  steveastrouk6 years ago
I'd like to make the simplest and least expensive system that will do the job. If a microcontroller fills that bill, then yes! But I don't know enough to say myself yet.
Well, I have a two chip solution for you, and I may even throw in a PCB design - it was an intriguing problem to lay out all the LEDs in a nice circle as an exercise !

Steve
tjerome (author)  steveastrouk6 years ago
Wow, that's great--thanks! What diameter did you use for the LED circle?

Ted
3"
tjerome (author)  steveastrouk6 years ago
OK; so how can I see what you have in mind? Am I missing a link you posted to your design?
Thanks in advance1
Ted
Here it is so far, its pretty well complete, apart from the wiring of the ATtiny168 at its heart. The idea is that the centre of the board is completely clear of wiring, and there's a 9/16 hole in the centre. I shall write it up and enter it into the competition I think.
60secarduino.jpg
tjerome (author)  steveastrouk6 years ago
Wow, that's beautiful! I'm eager to see your final version.
Cheers!
Ted
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